In spot-type disc brakes, new replacement linings are subject during break in to an increased tendency to radial lift out. In many cases, this may be due to the brakes failing to meet the specified dimensional tolerances or because the linings are mismatched to the brakes utilized. The frictional forces in radial and tangential directions which result from the surface of the lining being urged in a nonuniform way against the brake disc have a substantial effect contributing to the lift-out tendency of the lining. This may even lead to not only the lining being lifted out against a stop, but also to the generation of substantial forces acting through the lining on the brake housing which tend to radially lift the latter out of its guide. In extreme cases this may lead to the housing being lifted up into a rotating surface of the wheel within which the brake is mounted.
Aberrations in the entrance and exit portions of the linings also tend to cause the lifting-out of the linings, particularly if the lining extends over a relatively large sectorial angle of the brake disc.
These problems are discussed in more detail in the German patent application published without examination, No. 2,517,109.
As a remedy, it is known to chamfer the linings in a top layer along the lateral edges in the tangential direction. As is explained in more detail in the German patent application published without examination, No. 2,314,135, such chamfers moreover counteract any tendency for the lining to assume a tilted position in respect to the brake disc.
It is also known according to the French patent application published without examination, No. 7,516,750 (publication No. 2,312,690) to chamfer the lower edge in a tangential direction for purposes of noise reduction.
It will be appreciated that in principle, it is desirable that a relatively small portion of the lining be ground off during, in order to as quickly as possible cause the lining to be abutted against the brake disc uniformly and at a correct angle, so as to have an increased service life.
It is therefore the object of the invention to extend the service life of the brake linings and to minimize the duration of the brake-in period.